I. Field
The present disclosure relates generally to electronics, and more specifically to a digital phase-locked loop (DPLL) with two-point modulation.
II. Background
A DPLL is a circuit commonly used to adjust the frequency and/or phase of an oscillator. In one common application, a DPLL may be used to lock the frequency and/or phase of an oscillator to a reference signal having a precise frequency.
In another application, a DPLL may be used to modulate the frequency and/or phase of an oscillator with a modulating signal. If the bandwidth of the modulating signal is much smaller than a closed-loop bandwidth of the DPLL, then the modulating signal may be applied prior to a loop filter within the DPLL. However, if the bandwidth of the modulating signal is wider than the closed-loop bandwidth, then two-point modulation may be performed. For two-point modulation, the modulating signal may be applied to two modulation paths in the DPLL—one modulation path for narrowband modulation and another modulation path for wideband modulation. Two-point modulation may be used to effectively increase the bandwidth of the DPLL, so that the oscillator can be frequency modulated with a wideband modulating signal while minimally disturbing the normal operation of the DPLL.